Studies are planned of phagocytosis, for the most part of bacteria, by polymorphonuclear leukocytes. The research plan is particularly aimed at the relationships among specific but overlapping areas of leukocyte activity: particle ingestion per se, the increased metabolic activity that ordinarily accompanies phagocytosis, degranulation of lysosomal structures in leukocytes, and intracellular killing. The ways in which these activities can be separated from one another may distinguish obligate interactions from mere concomitance, and may reveal the specific pathways by which cell function is altered. The experimental approach will be through various agents and situations in which one or more of these activities are known to be altered, including 1) leukocytes treated with metabolic inhibiters such as iodoacetate, 2) leukocytes from patients with chronic granulomatous disease of childhood, 3) leukocytes fed particles of very small diameter, and 4) leukocytes treated with colchicine and other mitotic inhibiters that produce particular ultrastructural alterations. From the viewpoint of comparative cell physiology, this last group of substances will also be studied as they affect the movement of melanin granules in melanocytes and the separation of chromosomes in dividing cells--two systems in which these antimitotic agents produce ultrastructural changes similar to those seen in leukocytes.